One type of conventional transaxle assembly is described in Japanese Unexamined Patent Publication No. Hei 2(1990)-286954. The transaxle assembly includes a planetary gear unit and a differential. The planetary gear unit has a planetary gear set. The differential includes a differential case, a cross pin having ends at which are fixed a pinion gear and a pair of output shafts at each of which is fixed a side differential gear so as to engage one of the pinion gears. The planetary gear unit and the differential are arranged in series which is parallel with respect to the output shafts. This arrangement increases the length of the transaxle assembly along the direction of the shafts. If the planetary gear unit includes a plurality of planetary gear sets, with each planetary gear set being arranged in series so as to obtain a large shift ratio, the arrangement of the planetary gear unit further increases the length of the transaxle assembly. Thus, a large space is required to assemble the transaxle assembly into vehicles.
Another conventional transaxle assembly is described in SAE Technical Paper Series No. 850198 entitled "Design of a Two-Speed Automatic Transaxle for an Electric Vehicle". This transaxle assembly is shown in FIG. 3. The transaxle assembly 30 includes a planetary gear set 32 and a differential 31. The differential 31 has a differential case 31a, a cross pin 31b and a pair of output shaft 34, 35. The differential case 31a has a carrier portion 33 which is integrally formed with the differential case 31a. The carrier portion 33 extends outwardly from the differential case 31. The outer end of the carrier portion 33 receives a plurality of pinion pins 32a which each support a planetary gear 32b. The planetary gear set 32 and the differential 31 are arranged in parallel with respect to the axis of the output shafts 34, 35. Accordingly, this arrangement decreases the length of the transaxle assembly 30 along the direction of the shafts 34, 35. However, the carrier portion 33 of the transaxle assembly 30 is arranged around the differential case 31 such that the cross pin 31b has to be inserted through a small clearance between the planetary gears 32b when the transaxle assembly 30 is assembled. Therefore, a relatively long time is required to assemble the transaxle assembly 30 and the assembly can be somewhat difficult.